With a slim Republican majority now in the US Senate, President Bush is poised to quickly and efficiently fill most of 79 existing judicial vacancies.

As a result, the balance of power between Democratic and Republican appointees on the nation's powerful federal appeals courts is about to shift dramatically in the Republicans' favor.

Legal experts say there isn't much Democrats can do about it. And the prospect of a new crop of conservative judges has many liberal groups, including women's rights and abortion-rights organizations, on the defensive.

At the same time, many conservatives are celebrating. "The long night in the desert might finally be over," says Roger Pilon of the Cato Institute's Center for Constitutional Studies in Washington.

Mr. Pilon is referring to nearly 18 months of obstructionist tactics in the outgoing Democrat-controlled Senate, which had held up more than 50 of Mr. Bush's judicial nominees. "Once the 108th Congress comes in [in January], however, I should expect to see these nominations voted on, out, and up expeditiously," he says.

Issues winding through courts

The development comes amid an ongoing war on terrorism that has raised concerns in the US about whether the Bush administration has struck the proper balance between safeguarding national security and protecting civil liberties. In addition, all the major hot-button issues  reproductive rights, free speech, affirmative action, capital punishment  that work their way to the US Supreme Court arrive first at district and circuit courts.

With as few as seven strategically placed appointments to vacancies, the Bush administration would be in a position to establish a Republican-appointee majority among active judges on 11 of the 13 federal appeals courts.

Only the Second Circuit in New York and the Ninth Circuit in San Francisco would continue to maintain a majority of Democratic appointees among those courts' active judges.

Although the party affiliation of an appointing president is a crude measure of any one particular judge's judicial outlook or philosophy, in broad terms it illustrates the potential sweep of Bush's influence on the courts.

And it carries the promise of real power. Most federal appeals-court cases are decided by a randomly selected three-judge panel. But any one panel's decision can be reheard by an entire circuit court. Such "en banc" appeals can represent a second, crucial, level of appellate review in cases where, for example, two or three liberal judges on an individual panel issue a ruling that offends the conservative majority of judges in the circuit.

At present, the number of Democrat- and Republican-appointed judges is equal in three circuit courts: the Tenth Circuit in Denver, the Third Circuit in Philadelphia, and the District of Columbia Circuit in Washington.

There are four vacancies on the District of Columbia Circuit, and two on both the Third and Tenth Circuits.

The other key circuit court is the Sixth, based in Cincinnati. Democratic appointees hold a 6-to-3 advantage among active judges, but there are seven current vacancies on the court.

"This will open the door to a real shift in the balance of the courts toward a very conservative direction," says Michael Gerhardt, a professor at William & Mary Law School in Williamsburg, Va., and an expert in judicial selection.

'The final say'

"The appellate courts are important because as a practical matter they have the final say in most matters of law," Mr. Gerhardt adds. "The US Supreme Court decides only a small number of cases."

Although the most dramatic and immediate impact will be at the appeals-court level, the Republican edge in the Senate also presents an opportunity to fill any openings that might arise at the US Supreme Court.

"It changes the dynamic," says Jay Sekulow, chief counsel of the American Center for Law and Justice, a conservative public-interest law group in Virginia Beach, Va. "If there is a retirement from the Supreme Court, clearly to have the Senate Judiciary Committee controlled by the Republican Party will assist the president."

Mr. Sekulow adds that Democratic senators may be reluctant to engage in blatantly obstructionist tactics, given the Republican victories on Tuesday. "This was quite a mandate the president got," he says.

Senate Democrats could attempt to filibuster judicial-nominee votes. But analysts say that could be difficult.

"The Democrats will select their battles carefully," says Sheldon Goldman, a political-science professor at the University of Massachusetts at Amherst. "I am sure they would be able to successfully filibuster several of the nominees they believe are more extreme."